What do contractions feel like? How will I know when I go into Labor?

I'm a FTM and I'm 30 weeks. As the birth of our baby is getting closer, I get more worried about everything! Last night, I had a lot of pressure in my hips and vagina and felt a few of what felt like a WAY more intense Braxton Hicks. My belly kept tightening up, way worse than BH, and tighter than I thought it could. And they hurt. My lower back was hurting really bad. This was after sex. So idk what was going on and idk what labor feels like or contractions! Help!